Hydraulic stretch levelling machine

ABSTRACT

Hydraulic stretch levelling machines have a stretch gripper head which is powered by a hydraulic piston and cylinder drive unit in order to stretch level a workpiece; the other end of the workpiece is secured by a counter gripper head which includes an anchoring mechanism for anchoring it in position and which is adjustable at discrete intervals for allowing for different sizes of workpiece. I propose separating the anchoring mechanism from the counter gripper head and connecting the counter gripper head to the anchoring mechanism by steplessly variable connecting means so that the position of the counter gripper head can be steplessly variable in order to allow for different lengths of workpiece and in order to bring the workpiece properly between the jaws of the gripper head, without using the hydraulic piston and cylinder drive unit for this purpose.

Waited States Patent [1 1 Kost 51 Sept. 11, 1973 1 HYDRAULIC STRETCH LEVELLING MACHINE [76] lnventor: Erwin Kost, Dahlienpfad 10,

Osterath, Germany [22] Filed: Apr. 6, 1972 [211 Appl. No.: 241,625

[30] Foreign Application Priority Data Apr. 7, 1971 Germany P 21 17 104.0

[52] US. Cl. 72/311, 72/302 [51] Int. Cl B21d 11/04 [58] Field of Search 72/293, 295, 302, 72/305, 311; 24/263 HW [56] References Cited UNITED STATES PATENTS 3,595,057 7/1971 MacKenzie 72/302 3,349,598 10/1967 Pollak 72/295 3,172,528 3/1965 Smith 72/302 2,908,316 10/1959 Albers 72/302 2,715,431 8/1955 Grossu 72/302 3,475,943 11/1969 Otto-Claussen 72/297 Primary Examiner-Richard J. Herbst Assistant Examiner- M. .1. Keenan Att0rneyJohn C. Holman and Marvin R. Stern [57] ABSTRACT Hydraulic stretch levelling machines have a stretch gripper head which is powered by a hydraulic piston and cylinder drive unit in order to stretch level a workpiece; the other end of the workpiece is secured by a counter gripper head which includes an anchoring mechanism for anchoring it in position and which is adjustable at discrete intervals for allowing for different sizes of workpiece. I propose separating the anchoring mechanism from the counter gripper head and connecting the counter gripper head to the anchoring mechanism by steplessly variable connecting means so that the position of the counter gripper head can be steplessly variable in order to allow for'different lengths of workpiece and in order to bring the workpiece properly between the jaws of the gripper head, without using the hydraulic piston and cylinder drive unit for this purpose.

10 Claims, 5 Drawing Figures Patented Sept. 11, 1973 3 Sheets-Sheet 1 Patented Sept. 11, 1973 3 Sheets-Sheet 2 e t MN Q: N we m L Mr//Ar// 7 4 7 fir mN RN um Patented Sept. 11, 1973 3,757,557 r 3 Sheets-Sheet 5 a 3 f N Z Z w. M 4 1% AFR HYDRAULKC STRETCH LEVELLTNG MAQHINE The invention relates to a hydraulic stretch levelling machine for stretching workpieces such as sections and plate, the machine having a stretch gripper head which is movable in the stretch levelling direction for stretching a workpiece and is connected (directly or e.g. through cross members and tie-rods) to a hydraulic piston and cylinder driving means (and normally to the piston thereof), and a co-operating counter gripper head which is adjustable at discrete intervals in the stretch levelling direction and has engageable and diS- engageable anchoring means; the machine has means for adjusting the distance apart of the gripper heads, and also force transmitting means such as frames, columns or metallic tie members which can be embedded in foundations and have anchoring projections, anchoring recesses or anchoring apertures disposed at intervals to obtain the adjustment of the counter gripper head.

The distances between anchoring projections, anchoring recesses or anchoring apertures for anchoring the counter gripper head are generally designed in accordance with the maximum expected variations in length of the workpieces which are to be stretchlevelled on the stretch levelling machine. However, in manufacturing programmes yielding workpieces with relatively small variations in length and whose crosssections are large and therefore require large stretch levelling forces, the mechanical strength of the workpiece cross-sections remaining between the anchoring recesses or anchoring apertures in the frame or tie members can define the magnitude of the distances between anchoring positions.

The maximum length of stroke of the stretch gripper head or of the hydraulic piston and cylinder driving means in such hydraulic stretch leveller machines is equal to the length of stretching stroke of the stretch gripper head, which length corresponds to the maximum stretch of the longest workpiece which is to be stretched, plus the length of approach stroke, which latter length is equal to twice the approach length or clamping length of the workpiece in the gripper head plus the distance between the anchoring positions.

The length of stroke in such hydraulic cylinder piston driving means, which are adapted to exert large stretch levelling forces during the stretching stroke, must be increased by a length equal to the length of the approach stroke; the approach stroke however requires substantially smaller forces. The acquisition, operation and maintenance of hydraulic cylinder piston drive units (driving means) with a long piston stroke is expensive.

The distances between anchoring positions are made as short as, and in many cases shorter than, would be required by the maximum workpiece length deviations within any one manufacturing programme, with due reference to the length of the piston and cylinder driving means. In such cases, it is necessary for the workpieces of a manufacturing programme to be presorted in accordance with the distances between anchoring positions, an operation suffering from the disadvantage of requiring not only the removal from the production run of workpieces of excess or insufficient length, thus interrupting the uniform succession of workpieces, but also having the disadvantage of requiring suitable storage facilities and therefore space for storing the graded workpieces. Moreover, the operating process must be interrupted and a separate operation must be interposed for stretch levelling the graded workpieces, since the counter gripper head must be reset by an amount corresponding to the distance between anchoring positions and must be anchored at that position.

A further disadvantage of stretch levelling machines with a hydraulic piston and cylinder driving means which performs the stretch levelling stroke as well as the approach stroke, is due to the fact that the workpieces are gripped first by the stretch gripper head of the stretch levelling machine, since the workpieces are supplied to the stretch levelling machine with one end (usually the front end) aligned at a unifonn distance from the stretch gripper head, the workpieces being then pushed by the stretch gripper head over workpiece supports into the counter gripper head, in some circumstances over a distance corresponding to the length of one gripper and over a distance corresponding to the distance between anchoring positions. This results in score marks appearing, particularly on workpieces made of non-ferrous metals.

The present invention provides a hydraulic stretch levelling machine having a stretch gripper head which is movable in a stretch levelling direction for stretching a workpiece,

a hydraulic piston and cylinder driving means connected to the stretch gripper head for retracting the stretch gripper head to stretch a workpiece,

a co-operating counter gripper head, which is movable in the stretch levelling direction towards and away from the stretch gripper head,

engageable and disengageable anchoring means for anchoring the counter gripper head in one of a plurality of spaced positions which are different distances from the stretch gripper head, the anchoring means being movable in the stretch levelling direction, independently of the counter gripper head, and

connecting means connecting the counter gripper head to the anchoring means, the connecting means being steplessly variable in the stretch levelling direction to permit the distance of the counter gripper head from the anchoring means to be altered.

Thus, in accordance with the invention, the counter gripper head is separated from the anchoring means and is connected thereto by connecting means which may be adjusted in the stretch levelling direction; the position of the counter gripper head can be altered in that it may be detachably joined to the anchoring means, e.g. through one tie-rod or a number of parallel tie-rods extending in the stretch levelling direction and for instance connected directly to the counter gripper head.

The invention can thus avoid the disadvantages referred to above because the length of stroke of the hydraulic stretch piston and cylinder driving means and its structural length need only be defined by the stretch levelling stroke, which must be performed with a large force, and need not take account of the approach stroke, which requires only small forces; the approach stroke is no longer performed by the stretch gripper head or the hydraulic stretch piston and cylinder driving means, but by the counter gripper head.

Since the counter gripper head must be steplessly moved in the shortest possible time, in particular for the approach stroke, and must be reliably locked or anchored for the stretch levelling operation, the connecting means (which may be referred to as a retaining device) should be capable of rapid and simple adjustment and must be capable of holding the counter gripper head at any distance from the stretch gripper head.

if the adjustable connecting means includes at least one tie-rod extending in the stretch levelling direction, it is possible to use various clamping means for round andsmooth rods, for transmitting forces in the direction of the rod axis, the clamping means comprising split cylindrical bushes (split on one side) or comprising two half shells of various lengths, depending on the magnitude of the forces to be transmitted, for clamping the rod on one or both longitudinal sides by means of one or more screw-fastening connections. However, clamping means of this kind are not preferred for the present invention for various reasons. It is diflicult or almost impossible for the screw-fastening connections to be uniformly tightened, particularly if they include several screw-fastenings, so that the same axial force is always produced in each screw-fastening connection. Furthermore, bushes with slits or half shells are irregularly deformed over their length and circumference when the screw-fastenings are applied so that they do not grip the rod or rods with a uniform clamping pressure over the clamping length and clamping circumference and it is possible for high local contact pressures to occur; for reasons of safety such clamping means are usually constructed to a very large size. Furthermore, the screw threads of the screw-fastening connections are subject to a high rate of wear in uninterrupted operation, and the requirement that all screwfastenings must be simultaneously stressable or detachable with the same axial force involves substantial expense. Accordingly, clamping means of the kind described hereinabove are not generally suitable for adjustable connecting means (retaining devices) which must be actuated rapidly and in succession without interruption.

It is therefore preferred to have at least one pressure fluid actuated clamping means surrounding the tie-rod for clamping the tie-rod on all sides with substantially uniform compressive force and for releasing the rod to alter the distance between the counter gripper head and the anchoring means. Clamping means of this kind act from the exterior towards the interior and have an annular cylindrical pressure chamber and a cylindrical, resilient sleeve seal, the external periphery of which can be acted on by a pressure medium. The internal periphery of the sleeve seal engages a circular crosssection clamping sleeve having axial gaps, or individual clamping segments having axial gaps disposed therebetween, the clamping sleeve or segments being constructed of a material which is harder than that of the sleeve seal material.

The stretch levelling machine can include a hydraulic piston and cylinder driving means for moving the counter gripper head in and opposed to the stretch levelling direction if the distances between the anchoring positions are not excessively long, the hydraulic piston and cylinder driving means being just sufficiently pow erful for the stepless movement of the counter gripper head. However, for long distances between anchoring positions, it is more appropriate to use at least one motor connected to at least one running wheel of the counter gripper head. The position of the anchoring means may likewise be adjustable by means of at least one motor. it is preferred that the motors be hydraulic motors. The motors can be connected to the wheels by suitable gear trains.

The use of hydraulic stretch levelling machine moving parts driven solely by hydraulic pressure has the advantage that known and tried hydraulic regulating and control devices, which may be simply manually or automaticaily operated, may be employed for the control system as well as for regulating the operating functions of the hydraulic stretch levelling machine.

One embodiment of a hydraulic stretch levelling machine in accordance with the invention is shown diagrammatically in the accompanying drawings, in which:

FlG. 1 is a side view of the hydraulic stretch levelling machine;

FIG. 2 is a plan view of the hydraulic stretch levelling machine;

FIG. 3 is a side view of the hydraulic stretch levelling machine with its counter gripper head in its forward position;

FIG. 4 is a side view through an alternative counter gripper head and anchoring means; and

FIG. 5 is a longitudinal section through a side view of a hydraulic retaining device, on a larger scale.

A stretch gripper head 3 is disposed on the left-hand side of a foundation 1 and has wheels 3a, 3b, 3c, 3d running on rails 2a, 2b; the gripper head 3 is driven, via a piston rod 5, by a stationary stretch piston and cylinder drive mechanism having a cylinder 4a and a piston 4b, and hydraulic ducts 4c and M. A co-operating counter gripper head 6 is disposed on the right-hand side and has wheels 6a, 6b, dc, 6d; the gripper head 6 is connected via joints 7, a tie-rod 8 and connecting means in the form of a hydraulic retaining device it), to anchoring means 9, the anchoring means 9 running on wheels 9a, 9b, 9c, 9d. The hydraulic retaining device Ill, fixed in the anchoring means 9, connects the gripper head 6 to the anchoring means 9 by means of clamping means 20, 21, 22 (see H6. 5, described in more detail below) which grip around the tie rod 3.

When the hydraulic retaining device 10 is released, the gripper head 10 can be steplessly traversed towards the stretch gripper head 3 by means of a hydraulic piston drive mechanism H, 12, 12a having a cylinder 11 and a piston 12 with a piston rod 12a, the drive mechanism 11 being disposed between the anchoring means 9 and the gripper head 6 (see FIGS. 1 and 2). The anchoring means 9 is anchored in the stretch levelling direction by means of an engageable and disengageable wedge or key 14 which engages in corresponding recesses 16 in a metallic tie member 15, fixed to the foundation. There is a device (not shown) for actuating the wedge or key 14.

The front pair of wheels 9a, 9b is driven through gears 18a, 18b by one or more motors 17a and 17b, for example hydraulic motors, (which motors may be coupled by a cross-shaft 18) in order to enable the anchoring means 9 to be traversed from one anchoring recess 16 to another after the wedge or key 14 is disengaged.

As shown in FIG. 4, the counter gripper head 25 may alternatively be adjusted by means of motors, for example hydraulic motors 26, which drive the wheels 6c, dd. This method of drive is selected if there are great distances V between anchoring positions in the tie members 15, because in such a case long piston and cylinder drive mechanisms, even if constructed for small forces, are too expensive due to the great length, and in some circumstances such drive mechanisms cannot be constructed at all.

Thehydraulic retaining device (FIGS. 1 and 5) has a hollow hydraulic member 19 both ends of which have hydraulic clamping means 20, 21, 22 incorporated therein, which clamping means comprise substantially an annular cylindrical pressure chamber 20, a cylindrical sealing sleeve 21 and radially sliding metallic segments 22. One such clamping means is described in more detail in German Offenlegungschrift No. 1,922,497.

Metal or plastics bearing shells 24 are provided at each end of the retaining device 10 in flange covers 23, to function as guides and supports for the tie-rod 8;-the flange covers 23 are bolted onto the hollow members 19 and provide axial end closures to the annular cylindrical pressure chambers at the ends of the hollow member 19. i

If the tie-rod 8 is very long, the retaining device 10 (and hence the hollow member 19) may be of a suitable le ngth or a plurality of retaining devices 10 may be disposed end to end.

The method of operation of the hydraulic stretch levelling machine, the anchoring means of which are separated from the counter gripper head, is as follows:

FIG. 1 shows, by way of example and in simplified form, a workpiece 13 in the position in which it is offered to the stretch levelling machine. The distance A between the front end of the workpiece 13 and the front edge of the stretch gripper head is in operation kept as small and as constant as possible while the distance B between the rear end of the workpiece l3 arid the front edge of the counter gripper head 6 depends on the length of the workpiece, the distance B being determined by the magnitude of the severed and so-called lost end and the maximum distance B being equal to the anchoring distance V.

When the hydraulic stretch levelling machine is put into operation, the anchoring means 9 are first traversed by means of the hydraulic motors 17a, 17b until it is'over a recess 16 which corresponds to the length of the workpiece which is to be stretched levelled, whereupon the wedge or key 14 is engaged. When the workpiece 13 has been moved into the stretch levelling axis and the stretch gripper head 3 has been driven out into the initial stretch levelling position by means of the hydraulic cylinder piston drive mechanism 40, 4b as shown in FIG. 1, the counter gripper head 6 is traversed towards the stretch gripper head 3 either by means of the hydraulic stretch cylinder piston drive mechanism 11, 12, 12a or by means of the hydraulic motors 26.

After displacement through the distance B and through the clamping length E (see FIG. 1) over the rear end of the workpiece 13, the workpiece is gripped by'the hydraulically actuated gripper jaws 6e, 6f of the counter gripper head 6. In the present example, the

workpiece 13 (see FIG. 3) bears against a stop abutworkpiece 13 is subsequently stretch levelled after hydraulic fluid is supplied through the duct 4c into the cylinder piston drive mechanism 4a, 4b.

All embodiments can be arranged to be operated completely automatically so that all machine functions required for stretch levelling a workpiece may be initiated by means of a single operating knob.

I claim:

1. A hydraulic stretch levelling machine comprising a stretch gripper head which is movable in a stretch levelling direction for stretching a workpiece,

a hydraulic piston and cylinder driving means connected to the stretch gripper head for retracting the stretch gripper head to stretch a workpiece,

a co-operating counter gripper head, which is movable in the stretch levelling direction towards and away from the stretch gripper head,

engageable and disengageable anchoring means for anchoring the counter gripper head in one of a plurality of spaced positions which are different distances from the stretch gripper head, the anchoring means being movable in the stretch levelling direction, independently of the counter gripper head, and

connecting means connecting the counter gripper head to the anchoring means, the connecting means being steplessly variable in the stretch levelling direcu'on to permit the distance of the counter gripper head from the anchoring means to be altered.

2 A hydraulic stretch levelling machine as claimed in claim 1, wherein the adjustable connecting means includes at least one tie-rod extending in the stretch levelling direction and at least one pressure fluid actuated clamping means surrounding the tie-rod for clamping the tie-rod on all sides with substantially uniform compressive force and for releasing the rod to alter the distance between the counter gripper head and the anchoring means.

3. A hydraulic stretch levelling machine as claimed in claim 1, and further comprising a hydraulic piston and cylinder driving means for moving the counter gripper head in and opposed to the stretch levelling direction.

4. A hydraulic stretch levelling machine as claimed in claim 2, and further comprising a hydraulic piston and cylinder driving means for moving the counter gripper head in and opposed to the stretch levelling direction.

5. A hydraulic stretch levelling machine as claimed in claim 1, and further comprising wheels on the counter gripper head, on which wheels the counter gripper head runs during its movementin and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the counter gripper head in and opposed to the stretch levelling direction.

6. A hydraulic stretch levelling machine as claimed in claim 2, and further comprising wheels on the counter gripper head, on which wheels the counter gripper head runs during its movement in and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the counter gripper head in and opposed to the stretch le'velling direction.

7. A hydraulic stretch levelling machine as claimed I in claim 1, and further comprising wheels on the anchoring means, on which wheels the anchoring means levelling direction, and at least one motor connected to at least one of the wheels, for moving the anchoring means in and opposed to the stretch levelling direction. 9. A hydraulic stretch levelling machine as claimed in claim 5, wherein said motor is a hydraulic motor.

10. A hydraulic stretch levelling machine as claimed in claim 7, wherein said motor is a hydraulic motor.

* i i l UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,757,557 Dated Se gtember 11, 1973 Inventor s) ERWIN KOST It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[73] Assignment data Schloemann Aktiengesellschaft Dusseldorf, Germany Column 1, line 2, insert heading BACKGROUND OF THE INVEN- TION-. 7

Column 1, lines 30 and 31, cancel "the mechanical strength of the workpiece cross-sections remaining", insert the distance between anchoring positions should be small. However,

in such cases sufficient material must remain-- Column l, lines 32 and 33, cancel "in the frame or tie members" and-insert to take up a reaction force which is equal to--.

Column 1, line 34, cancel "positions", insert recesses or apertures- Column 1, line 33, before "can", insert the stretching force, and the cross-section required for this material-.

Column 1, line 33, cancel "define", insert -dictate.

Column 2, after line 22, insert heading SUMMARY OF THE INVEN- TION.

Column 2, line 42, before "in", insert in length--.

FORM PO-IOSO (10-69) USCOMM'DC 60376-P69 US, GOVERNMENT PRINTING OFFIGE: I969 O366-33 CERTIFICATE OF CORRECTION Patent 3.757.557 Dated September 11. 1973 Inventor(s) ERWIN KOS'I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 44, cancel "alter", insert permit alterations of--.

Column 4, after line 10,. insert heading -BRIEF DESCRIPTION OF THE DRAWINGS.

Column 4, after line 24, insert heading -DE'IAILED DESCRIPTION OF THE PREFERRED EMBODIMENT.

Column 4, line 42, before "gripper", insert -'-counter--; same line, cancel "l0", insert --6.

Column 5, line 43, cancel "When", insert -Following this,-.

Column 5, line 44, cancel "has been", insert --is--.

Column 5, line 45, cancel "and", insert a comma Column 5, line 48, after "FIG. 1,", insert and--.

line 26, before "in", insert -in length-. Claim 2, line 37, cancel "alter", insert -permit alteration of-.

Signed and sealed this 25th day of June 19714..

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents )RM PO-1050 (10-69) USCOMM-DC 60376-P69 9 U.5. GOVERNMENT PRINTING OFFICE: I959 0-366-334 

1. A hydraulic stretch levelling machine comprising a stretch gripper head which is movable in a stretch levelling direction for stretching a workpiece, a hydraulic piston and cylinder driving means connected to the stretch gripper head for retracting the stretch gripper head to stretch a workpiece, a co-operating counter gripper head, which is movable in the stretch levelling direction towards and away from the stretch gripper head, engageable and disengageable anchoring means for anchoring the counter gripper head in one of a plurality of spaced positions which are different distances from the stretch gripper head, the anchoring means being movable in the stretch levelling direction, independently of the counter gripper head, and connecting means connecting the counter gripper head to the anchoring means, the connecting means being steplessly variable in the stretch leVelling direction to permit the distance of the counter gripper head from the anchoring means to be altered.
 2. A hydraulic stretch levelling machine as claimed in claim 1, wherein the adjustable connecting means includes at least one tie-rod extending in the stretch levelling direction and at least one pressure fluid actuated clamping means surrounding the tie-rod for clamping the tie-rod on all sides with substantially uniform compressive force and for releasing the rod to alter the distance between the counter gripper head and the anchoring means.
 3. A hydraulic stretch levelling machine as claimed in claim 1, and further comprising a hydraulic piston and cylinder driving means for moving the counter gripper head in and opposed to the stretch levelling direction.
 4. A hydraulic stretch levelling machine as claimed in claim 2, and further comprising a hydraulic piston and cylinder driving means for moving the counter gripper head in and opposed to the stretch levelling direction.
 5. A hydraulic stretch levelling machine as claimed in claim 1, and further comprising wheels on the counter gripper head, on which wheels the counter gripper head runs during its movement in and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the counter gripper head in and opposed to the stretch levelling direction.
 6. A hydraulic stretch levelling machine as claimed in claim 2, and further comprising wheels on the counter gripper head, on which wheels the counter gripper head runs during its movement in and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the counter gripper head in and opposed to the stretch levelling direction.
 7. A hydraulic stretch levelling machine as claimed in claim 1, and further comprising wheels on the anchoring means, on which wheels the anchoring means runs during its movement in and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the anchoring means in and opposed to the stretch levelling direction.
 8. A hydraulic stretch levelling machine as claimed in claim 4, and further comprising wheels on the anchoring means, on which wheels the anchoring means runs during its movement in and opposed to the stretch levelling direction, and at least one motor connected to at least one of the wheels, for moving the anchoring means in and opposed to the stretch levelling direction.
 9. A hydraulic stretch levelling machine as claimed in claim 5, wherein said motor is a hydraulic motor.
 10. A hydraulic stretch levelling machine as claimed in claim 7, wherein said motor is a hydraulic motor. 